Echo from wait loop, not job callback

This makes the pager behave a better, allowing the -- More -- prompt to
actually display and not dropping output if the process exits while
there's a backlog.  An additional benefit is if Git for some reason
produces additional output while GIT_EDITOR is running, that output will
be buffered rather than interrupting the user.

The extracted s:RunTick() helper changes the Vim behavior to check the
process status after waiting as well as before.  This brings it in line
with how Neovim's jobwait() appears to work.

The zero argument :echo after the final s:RunEcho() clears up some weird
draw issues with `:Git command|someothercommand`.

References https://github.com/tpope/vim-fugitive/issues/1717

autoload/fugitive.vim

@@ -2421,8 +2421,8 @@ function! s:RunEdit(state, tmp, job) abort
 endfunction
 
 function! s:RunReceive(state, tmp, type, job, data, ...) abort
-  let data = type(a:data) == type([]) ? join(a:data, "\n") : a:data
   if a:type ==# 'err' || a:state.pty
+    let data = type(a:data) == type([]) ? join(a:data, "\n") : a:data
     let data = a:tmp.escape . data
     let escape = "\033]51;[^\007]*"
     let a:tmp.escape = matchstr(data, escape . '$')
@@ -2447,12 +2447,12 @@ function! s:RunReceive(state, tmp, type, job, data, ...) abort
     let lines[-1] = ''
   endif
   call writefile(lines, a:state.file, 'ba')
-  let data = a:tmp.echo . data
+  if has_key(a:tmp, 'echo')
-  let a:tmp.echo = matchstr(data, "[\r\n]\\+$")
+    if !exists('l:data')
-  if len(a:tmp.echo)
+      let data = type(a:data) == type([]) ? join(a:data, "\n") : a:data
-    let data = strpart(data, 0, len(data) - len(a:tmp.echo))
+    endif
+    let a:tmp.echo .= data
   endif
-  echon substitute(data, "\r\\ze\n", '', 'g')
 endfunction
 
 function! s:RunExit(state, tmp, job, exit_status) abort
@@ -2489,16 +2489,32 @@ function! s:RunSend(job, str) abort
   endtry
 endfunction
 
+function! s:RunEcho(tmp) abort
+  let data = a:tmp.echo
+  let a:tmp.echo = matchstr(data, "[\r\n]\\+$")
+  if len(a:tmp.echo)
+    let data = strpart(data, 0, len(data) - len(a:tmp.echo))
+  endif
+  echon substitute(data, "\r\\ze\n", '', 'g')
+endfunction
+
+function! s:RunTick(job) abort
+  if type(a:job) == v:t_number
+    return jobwait([a:job], 1)[0] == -1
+  elseif type(a:job) == v:t_job && (ch_status(a:job) !=# 'closed' || job_status(a:job) ==# 'run')
+    sleep 1m
+    return ch_status(a:job) !=# 'closed' || job_status(a:job) ==# 'run'
+  endif
+endfunction
+
 if !exists('s:edit_jobs')
   let s:edit_jobs = {}
 endif
 function! s:RunWait(state, tmp, job) abort
   let finished = 0
   try
-    while get(a:state, 'request', '') !=# 'edit' && (type(a:job) == type(0) ? jobwait([a:job], 1)[0] == -1 : ch_status(a:job) !=# 'closed' || job_status(a:job) ==# 'run')
+    while get(a:state, 'request', '') !=# 'edit' && s:RunTick(a:job)
-      if !exists('*jobwait')
+      call s:RunEcho(a:tmp)
-        sleep 1m
-      endif
       if !get(a:state, 'closed_in')
         let peek = getchar(1)
         if peek != 0 && !(has('win32') && peek == 128)
@@ -2520,7 +2536,7 @@ function! s:RunWait(state, tmp, job) abort
         endif
       endif
     endwhile
-    sleep 1m
+    call s:RunEcho(a:tmp)
     echo
     call s:RunEdit(a:state, a:tmp, a:job)
     let finished = 1